A. Gas atoms subjected to electricity emit bright lines of light
Explanation:
When subjected to electricity, the electrons of a gas atom are <em>excited</em>. From that excited energy level, the electrons eventually go back to their initial state; this <u>transition</u> is done by emitting photons at a specific wavelength (causing an emission of bright lines of light).
Such is the mechanism of gas-discharge lamps tipically found in households.
